Consolidated Statements of Changes in Stockholders' Equity (Unaudited) - USD ($) $ in Thousands		Total	Performance/Service Based RSAs, RSA,	Board Authorized Purchase Program [Member]	Series C Preferred Stock	Series D Preferred Stock	Series E Preferred Stock	Preferred Equity	Common Stock	Surplus	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Treasury Stock	Treasury Stock Performance/Service Based RSAs, RSA,	Treasury Stock Board Authorized Purchase Program [Member]
Beginning balance at Dec. 31, 2018		$ 3,780,888						$ 256,716	$ 1,752	$ 1,712,615	$ 2,181,414	$ (124,972)	$ (246,638)
Comprehensive income
Net income		86,686									86,686
Other comprehensive income (loss)		21,597										21,597
Comprehensive income		108,283
Common stock issued
Stock-based compensation plans, net		7,045								(32,220)			39,265
Purchase of treasury stock,			$ (7,468)	$ (29,999)										$ (7,468)	$ (29,999)
Cash dividends
Common stock ($0.17 per share in 2019 and $0.18 per share in 2020)		(28,183)									(28,183)
Preferred stock(a)	[1]	(3,801)									(3,801)
Stock-based compensation expense, net		9,397								9,397
Other		(293)									(293)
Ending balance at Mar. 31, 2019		3,835,870						256,716	1,752	1,689,792	2,235,824	(103,375)	(244,840)
Cash dividends
Preferred Stock, Dividends, Per Share, Cash Paid					$ 0.3828125	$ 0.3359375	$ 0.3671875
Cumulative effect of ASU 2016-13 adoption (CECL) | Accounting Standards Update 2016-13		(98,337)									(98,337)
Total shareholder's equity at beginning of period, as adjusted		3,823,787						256,716	1,752	1,716,431	2,282,530	(33,183)	(400,460)
Beginning balance at Dec. 31, 2019		3,922,124						256,716	1,752	1,716,431	2,380,867	(33,183)	(400,460)
Comprehensive income
Net income		45,838									45,838
Other comprehensive income (loss)		16,209										16,209
Comprehensive income		62,046
Common stock issued
Stock-based compensation plans, net		2,896								(20,659)			23,555
Purchase of treasury stock,			$ (5,555)	$ (71,255)										$ (5,555)	$ (71,255)
Cash dividends
Common stock ($0.17 per share in 2019 and $0.18 per share in 2020)		(28,392)									(28,392)
Preferred stock(a)	[1]	(3,801)									(3,801)
Stock-based compensation expense, net		10,744								10,744
Ending balance at Mar. 31, 2020		$ 3,790,471						$ 256,716	$ 1,752	$ 1,706,516	$ 2,296,176	$ (16,974)	$ (453,714)
Cash dividends
Preferred Stock, Dividends, Per Share, Cash Paid					$ 0.3828125	$ 0.3359375	$ 0.3671875

[1] (a) Series C, $0.3828125 per share; Series D, $0.3359375 per share; and Series E, $0.3671875 per share.